1. Field of the Invention
The present invention relates to compressors, and more particularly, to a reciprocating compressor having a piston for reciprocating in a cylinder to compress a working fluid.
2. Background of the Related Art
The compressor boosts a pressure of the working fluid by receiving a power from an electric motor or a turbine, and applying a compressive work to air, refrigerant, or other special gas. The compressor is widely used starting from home appliances, to plant industries in the fields of air conditioners, or refrigerators.
Depending on methods of compression, there are positive displacement compressors, and dynamic compressors, or turbo compressors. In the positive displacement compressors for boosting a pressure by reduction of a volume, there are reciprocating compressors, and rotary compressors.
The reciprocating compressor, compressing the working fluid by means of a piston reciprocating inside of a cylinder, is advantageous in that a high compression efficiency can be provided by using comparatively simple mechanical components.
The rotary compressor, compressing the working fluid by means of a roller revolved inside of a cylinder with an eccentricity, can provide a high compression efficiency at a speed lower than the reciprocating compressor.
FIG. 1 illustrates a typical example of the reciprocating compressor, referring to which the reciprocating compressor will be described in more detail.
Referring to FIG. 1, two pieces of cases 1 assembled together form an enclosed space, in which a frame 2 is provided. The frame 2 is supported on an inside of the case 1 with springs 4.
There is a crankshaft 6 mounted passed through a central part of the frame 2. For this, there is a boss 3 in the central part of the frame 2 for stable support of the crankshaft 6.
The crankshaft 6 mounted thus, is rotated by the motor 5 having a stator 5a and a rotor 5b. The stator 5a is fixed to the frame 2, and the rotor 5b is fixed to the crankshaft 6. Since the rotor 5b positions inside of the stator 5a, the crankshaft 6 rotates together with the rotor 5b when power is provided to the motor 5.
Referring to FIG. 1, there is an eccentric pin 6a on top of the crankshaft 6 at an eccentric position from a rotation center of the crankshaft 6. There is a balance weight 6b on top of the crankshaft at an opposite side of the eccentric pin 6a. The balance weight 6b prevents the crankshaft 6 from shaking due to weight of the eccentric pin 6a during rotation of the crankshaft 6.
In the meantime, there is lubricating oil held on a bottom of the case 1, and the crankshaft 6 has oil passages 6c inside of the crankshaft 6. Accordingly, when the crankshaft 6 rotates, lubricating oil moves following the oil passage 6c, and sprayed from the top of the crankshaft 6. According to this, the lubricating oil is supplied to all mechanically operative components in the case 1.
There are a cylinder 10 having a compression chamber 11 therein in one side part of top of the frame 2, and a piston 15 in the compression chamber 11 to reciprocate in the cylinder 10 when the crankshaft 6 is rotated by the connecting rod 7. For this, one end of the connecting rod 7 is connected to the eccentric pin 6a of the crankshaft 6, and the other end of the connecting rod 7 is coupled to the piston 15.
There is a valve assembly 20 mounted on an end of the cylinder 10 for controlling flow of a working fluid introduced into the compression chamber 11, compressed therein, and discharged therefrom, which will be described with reference to FIG. 2.
Referring to FIG. 2, the valve assembly 20 is provided with a valve plate 21, a suction valve 22, and a discharge valve 23.
The valve plate 21 has a suction hole 24 for introduction of the working fluid into the compression chamber 11, and a discharge hole 25 for discharging the working fluid to an outside of the compression chamber 11.
The suction valve 22 is between the cylinder 10 and the valve plate 21, for automatic opening/closing of the suction hole 24 according to a pressure change of the compression chamber 11. As shown in FIG. 2, the discharge hole 25 is provided, not only to the valve plate 21, but also to the suction valve 22.
The discharge valve 23 is provided to one surface of the valve plate 21 opposite to a surface the suction valve 22 is fitted thereto, for automatic opening/closing of the discharge hole 25 according to a pressure change of the compression chamber 11. As shown in FIG. 2, the suction hole is provided, not only to the valve plate 21, but also to the discharge valve 23.
In the meantime, there is a head assembly 30 on the valve assembly 20, more specifically, the discharge valve 23. Though not shown, there is a gasket between the head assembly 30 and the valve assembly 20, for preventing leakage of the working fluid, and pressure drop of the compression chamber. The head assembly 30 guides flow of the working fluid controlled by the valve assembly 20.
In the meantime, referring to FIG. 1, there is a suction muffler 13 connected to the head assembly 30, for attenuating noise of flow of the working fluid introduced into the compression chamber 11 through a suction pipe 12. There is a discharge pipe 14 connected to the head assembly 30 for discharge of the working fluid to an outside of the compression chamber through the discharge hole 25. Though not shown, there is a discharge muffler between the discharge pipe 14 and the head assembly 30 for attenuating noise from the working fluid.
In operation, upon application of power to the motor 5, the rotor 5b and the crankshaft 6 rotates, and the rotation of the crankshaft 6 is converted into linear reciprocating movement. According to this, the refrigerant introduced into the compressor through the suction pipe 12 is compressed by the piston reciprocating in the cylinder 10, and discharged to an outside of compressor through the discharge pipe 14.
Meanwhile, while above process is carried out, the piston 15 makes linear reciprocating movement within the cylinder 10 at a fast speed. In this instance, an inside wall of the cylinder 10, and an outside surface of the piston cause friction on each other, which drops an efficiency of the compressor due to a friction loss taken place in this time.
In the meantime, when the piston 15 is at a top dead center, a dead volume is formed, which has a size a top clearance existing between a top end of the piston 15 and the valve plate 21 and an inside volume of the discharge hole 25 are added together.
The dead volume formed thus drops the efficiency of the compressor. Therefore, it is preferable to minimize the dead volume.